The Duchess of Cornwall joined the Prince of Wales for a first trip on a new ultra-low carbon double-decker London bus today.

The royals toured the factory of Wrightbus in Ballymena, Northern Ireland, which is supplying 600 of the hybrid-engine vehicles to London in a contract worth more than £200million.. before taking a ride on one.

The firm has expanded massively in recent years and is known as one of the most innovative in Northern Ireland.

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Royal carriage: The Prince of Wales and Duchess of Cornwall took a ride on a new eco-friendly bus today

Is this our stop? The royals toured the factory of Wrightbus in Ballymena, Northern Ireland. The Duchess was dressed stylishly in navy and white

Robert Alexander, 64, has worked at the plant since he was 15, for 49 years.

He entertained the Prince with stories of how the factory had changed since he was an apprentice on the factory floor. He now checks the quality of outside supplies like seats, sheet metal and glass used in the construction of the state-of-the-art vehicles.

The new bus has a design similar to the old Routemaster. Route 24, which passes Parliament and Trafalgar Square, now uses the new vehicles exclusively.

Transport for London (TfL), the public body that manages transport in the capital, has said the new bus is the greenest diesel electric hybrid bus in the world.

TfL estimates the 600-strong fleet will reduce carbon dioxide emissions in the city by almost 20,000 tonnes a year.

Regal: The Duchess of Cornwall meets people in Broughshane County Antrim during her visit to the town

The Duchess of Cornwall tries a cut out bear mask made by schoolchildren from Broughshane Primary School

Peek-a-boo: read a story to the children and took part in the 'Goldilocks Rap'

Each bus costs about £354,500 and has an estimated lifespan of 14 years.

Later that day the Duchess helped show children that books were fun during a library in Broughshane, County Antrim.

The avid reader joined celebrity chef Jenny Bristow to make oatmeal muffins for scores of excited four-year-olds at the library. She is patron of a number of organisations which promote literacy throughout the UK.

Camilla helped bake some of the cakes, read a story to the children and took part in the 'Goldilocks Rap', tapping her hands lightly against her knee as the youngsters sang along.

Libraries NI chief executive Irene Knox said: 'It was a tremendous day for Broughshane Library and we are delighted that the Duchess emphasised the importance of books.

Cheeky: A boy sticks his tongue out as the Duchess of Cornwall bakes some porridge muffins with some help from schoolchildren

Camilla patronises the National Literacy Trust and BookTrust among other organisations

'She was very, very clear that reading and enjoying books is such an important skill for young children to have so she was encouraging children to read and encouraging the adults here to bring their children to libraries and to get them to read books as something that they could enjoy.

'I think today was a day of fun and it was really showing that libraries and books are fun.'

She patronises the National Literacy Trust and BookTrust among other organisations.

Camilla enthusiastically greeted a crowd of well-wishers brandishing Union flags by the roadside and was led to a white marquee outside the library where Ms Bristow was already expertly digging her spoon into dough and encouraging children to add strawberries to a sticky porridge mixture in a large bowl.

The Duchess, dressed in navy and white, stooped to admire their work.

Anne McAleese, nursery teacher at Broughshane Primary, said: 'It is lovely for the children, it is a real opportunity for them at their age to meet someone like that.'